The role of human intestinal brush-border membrane hydrolases in lectin binding to the apical region of the enterocyte was investigated. The crossed-immunoelectrophoresis method was used to identify six hydrolases before and after interaction with nine lectins. Three lectins (Phaseolus vulgaris, Ulex europeus, and Ricinus communis 120 agglutinins) bound the hydrolases of 5 different subjects. Helix pomatia agglutinin interacted with only 1 subject.